Apple private relay is very flawed but on the other hand most sites that view connections originating from VPN as suspicious seem to be ok with Apple Private Relay. If you have VPN on your router private relay on top of it could be a good way to do ip address laundering.
I find it pretty annoying that iCloud Private Relay does not work together with VPNs.
I mainly use VPNs to access bank sites (or other sites that are annoying enough to use IP country as a proxy for traffic being evil/legitimate) when traveling, but I often forget to turn off the VPN afterwards, and then spend the rest of my day browsing from my home IP (that terminates the VPN), which would have been hidden behind Private Relay if I'd actually been browsing from my home Wi-Fi.
Cross-site/app ad targeting getting creepy good despite using different browser profiles for work/personal browsing etc. is usually a good tell (at least on IPv6).